Combustion heater having air preheating and carbureting means



Nov. 2,1948. H. .1. DE N. MccoL u 2,452,779

COMBUSTIONHEATER HAVING AIR PREHEATING AND CARBURE'RING MEANS Filed Feb. 19, I943 Patented Nov. 2, 1948 'COMBUSTION HEATER HAVING AIR PRE- IIEATI-NG'AND" CARBURETING MEANS Henry'JlDe NIMCollum, Chicago, Ill.; Thelma McCcllum'executrix oi said Henry J. De N. Mc- Collumfdeceased. assignor to Stewart-'Warner Corporation, *Chicago, 111., a corporation of "-Virgiriia .Application February 19, 1943, Serial No. 476,430

lfClaim.

.1 My invention relates toiheaters and more particularly to heaters of the internal combustion 'l' ype, such as are commonl used for aircraft "andother vehicles and for generalpurposes.

'Infheaters of the internal combustion type to which my invention pertains, it is customary'to ,In such "heaters there-is a certain resistance to the how of air through the heater and Where these heaters are provided with the conventional carburetor utilizing a 'Venturi tube to suck fuel thereinto, thefresistan'ce .of the heater to flow of air therethrough is materially increased. Such increase 'of resistance is "objectionable in that a relatively high pressure ram or blower is required to supply the necessary amount of air for heater operation.

An object of my invention islto provide aheater 'which'ofiers'a'minimum resistance to flow of air "therethrough"andwhich can, therefore, .be operated ffrom a low pressure ram, blower, or other .s'ource of "airsupply.

- Another object of my invention is to provide "a heaterin whichthe conventional carburetor is eliminated and wherein fuel mixing .means is provided 'which offers a minimum of-res'istance .to airflow.

Another .object of my'inven'tion is to provide novel means "for mixing air and Ifuel toiorm a combustible "mixture and which will provide any desired degree ofpreheating.

Another object of my invention is to provide a .low resistance heater which is particular-"1y adapt ed 'for use in connection with a single low pressure blower, ram, or other means for supplying air to support combustion and for ventilating purposes.

Other objects and advantages will become apparent as the description proceeds.

In the drawings:

Fig. 1 is a somewhat diagrammatic view of a heater embodying a preferred form of my invention, parts of this heater being shown in iongitudinal section; and

Fig. 2 is a transverse, sectional view of the spinner of Fig; l and is taken on the line 2-2 of Fig. 1.

In Fig. 1 of the drawings, I have shown an internal combustion type or heater having'a coinbustion chamber [0 located in one end of atubular heat exchanger [2 of the type disclosed and claimed in my co-pending application, now Patent No. 2,380,602. The hot gases formed in the combustion chamber flow through the flues H extending lengthwise of the heat exchanger lzfa'nd are discharged into an outlet chamber l5 fro'm which the cooled gases pass to atmosphere through an outlet fitting l6 and any'suitable exhaust pipe attached'to the threaded end 18 of this fitting.

A muffler 20 is locate'din the heat exchanger l2 and comprisesa metal shell 22 containing sound absorbing material 24, such as stainless steel'wool or glass wool. Perforations 26 in'the shell 22 Iform acoustic 'couplingsbetween the flues l4 and the interior of the muffler shell, permitting sound to pass into the interior of this shell and be absorbed by the material 24 therein.

Theheater is enclosed in a casing 28 whose righthand o'r inlet end is connected to the outlet of a low pressure blower 30 which may be'driven by any suitable means. The blower 30 is illustrated as being of the centrifugal type, as this type of blower forms a highly eflicient and desirable low. pressure source of supplyfor my' novel heater.- It is to be understood, of course, that my invention'is not limited to use'with this particular type of blower or in fact with any blower, since the air required for heater operation may be supplied'by a ram or any other suitable means.

Most of the air supplied by the blower -30 passes over the fins 32 of the heat exchanger and is heated thereby. This heated air passes from'the lefthand end of the casing 28 into the airplane cabinor other space to be heated, or into a duct sytem having selected outlets located in the same or different cabins or other --enclose'd spaces, as may be desired. E

'Part of the air supplied by the blower 3llhas its direction reversed by an annular scoop 38 secured to the outer Wall of the combustion chamber. The diverted air flows into an annular space 34 provided between the outer wall of the combustion chamber and the inner wall of an annular skirt formed as a portion of a cap 36 which covers the combustion chamber end of the heat exchanger. The air entering the annular space 34 forms the air for the combustible mixture supplied to the combustion chamber II]. This combustion air flows rearwardly and thence radially inwardly over the end wall of the combustion chamber and is preheated before passing through the slots 4|] in a cup-shaped spinner 42. As shown.

most clearly in Fig. 2, the slots 40 are formed by punching and bending inwardly the tongues 44 which serve to give the air a whirling motion as it passes into the interior of the spinner 42. This whirling motion is in a plane perpendicular to the longitudinal axis of the heater and is clearl indicated by the arrows in Figs. 1 and 2.

A fuel jet 46- is located in the center of the spinner and delivers a rich mixture of fuel and air thereto through outlets 48. This rich mixture is picked up by the whirling air in the spinner which breaks up the rich mixture to form a thoroughly homogeneous mixture of air and fuel of the proper richness for efficient combustion. This latter mixture passes from the open left-hand end of the spinner into the combustion chamber, where it is initially ignited by the usual electrical igniter 56. The igniter may be cut out by the usual thermostatic switch after combustion has been initiated, and a re-igniter 52 is provided to maintain combustion thereafter.

I shall now describe the means for furnishing an exceedingly rich mixture of fuel and air to the jet 46. This means comprises a float bowi 54 connected by pipe 56 with any suitable source of fuel. The float bowl 54 is maintained under slight pressure by a ram 58 located in the heater inlet and projecting into the stream of air flowing to the heater from the blower or other suitable source of air supply. The ram communicates with the float bowl 54 by way of pipes 66 and T 62.

The bottom of the float bowl 54 communicates by way of restriction 64with a T 66. This T communicates with the ram 58 by way of pipes 68 and 68 and restriction T0. The T 66 also communicates with the jet 46 by a pipe 12. The restriction 70 is preferablyin the neighborhood of four times as large in cross section as the restriction 64.

This fuel supply means requires only a slight pressure differential for its operation so that the pressure at the ram 58 need be only slightly above the pressure at the jet 46. This is of particular importance where the heater is used as a ram supplied aircraft heater intended for operation at high altitudes under low atmospheric pressure and low air density and also where it is desired to operate the heater from a low pressure blower or other low pressure source of air supply.

The air pressure at the ram 58 is communicated to the float bowl 54 and this pressure, plus the hydrostatic head of the fuel in the float bowl forces the fuel through the restriction 64 into the T 66. Pressure in the ram 58 forces a small amount of air through pipes 60 and 68 and restriction 10 into T 66, where it mixes with the fuel flowing into this T through the restriction 64. The rich mixture of fuel and air thus formed flows through pipe 68 to jet 46. Since the pipe 12 contains a mixture of fuel and air instead of being filled with solid liquid fuel, only slight force 4 is required to lift this fuel and air mixture from the T 66 to the jet 46.

The interior of the spinner is in open communication with the combustion chamber and receives heat directly therefrom. This additional heat aids the preheated air in completely vaporizing the rich mixture of fuel and air supplied by the jet 46.

While I have illustrated a form of my invention, it is to be understood that my invention i not limited to the details shown and describedx but may assume numerous other forms and that, the scope of my invention is defined in the following claim.

I claim:

In a heater having a combustion chamber having a cylindrical wall and an end wall, and heat exchange means receiving hot products of combustion from the combustion chamber, the combination of a cup-shaped combustion air spinner attached to the end wall of the combustion chamber and in open communication with the combustion chamber, said spinner having a series of slots in the cylindrical wall thereof, an inwardly directed tongue associated with each of said slots to give the air passing therethrough a whirling motion, aplate spaced from the end wall and having a cylindrical portion in telescopic relation to and spaced from the cylindrical Wall, said plate enclosing said spinner, means forming a jet delivering at the axial center of said spinner and at a point spaced from the base thereof, means for supplying a rich mixture of fuel and air to said jet, and means for supplying preheated combustion air to said spinner by forcing said air between said plate and the combustion chamber walls.

HENRY J. DE N. MCCOLLUM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 248,110 Park et a1 Oct. 11, 1881 1,020,048 Normand Mar. 12, 1912 1,357,598 Thompson Nov. 2, 1920 1,536,046 Anthony May 5, 1925 1,583,238 Scudder May 4, 1926 2,000,733 Avery May 7, 1935 2,028,807 Reiboldt Jan. 28, 1936 2,039,890 Coster May 5, 1936 2,201,627 LaMont May 21, 1940 2,286,853 I-Iolthouse June 16, 1942 2,286,856 I-Iolthouse June 16, 1942 2,402,971 McCollum July 2, 1946 FOREIGN PATENTS Number Country Date 166,145 Switzerland Dec. 31, 1933 

